Dimerization process



United States Patent DINIERIZATION PROCESS Charles A. Cohen, Roselle Park, and Clifiord W. Muessig, Breton Woods, N. 1., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application December 31, 1953, Serial No. 401,691

4 Claims. (Cl. 260--683.15)

a This invention relates to a process for the dimerization of a C6 to C12 olefin to produce a higher molecular weight olefinic dimer thereof most selectively. More particularly, it relates to the dimerization of a C6 to C12 polymer of propylene which may be a narrow polymer fraction .of a simple propylene polymerization product but by definition said polymer fraction should contain only at least two but not more than four units of the simpler olefin in the polymer molecule. This specifically excludes the presence or addition of monomeric propylene during the desired dimerization. For the purpose of this invention, a catalyst comprising boron trifluoride (BFa) and an organic alkoxy type ether in the form of a complex is used with additional boron fluoride.

This application is a continuation-in-part of Serial Number 202,429, filed December 22, 1950, now abandoned.

In the practice of this invention, the reactant olefin, which is a C6 to C12 propylene polymer, is contacted with a preformed boron fluoride-ether complex as catalyst within the of .02 to 0.1 mole of catalyst complex per mole of feed while maintaining an excess of boron trifluoride in the reaction mixture. This excess of boron trifiuoride may be maintained up to the limit of its solubility in the reaction mixture at the operating temperature and pressure. The process as described is especially concerned with controlling the dimerization so as to obtain a relatively high conversion of 2. Ce to C12 polymer to a dimeric polymer, and this essentially involves preventing reaction of the C6 to C12 polymer with C3 monomer.

In a preferred practice of this invention, a C6 to C12 fraction of polypropylene, either in boiling individual fractions or as a somewhat wide boiling fraction, encompassing material boiling within the range C6-C12 polypropylene, is dimerized to a C12 to C24. polypropylene by means of the boron fluoride-ether catalyst complex. Olefins of which the C12 to C24 polypropylenes are typical examples, find use in the production of synthetic detergents, oil soluble sulfonates, lubricating oil additives, alkyl mercaptans, feeds for the 0x0 reaction in which higher aldehydes, acids and alcohols are formed and in other higher alkyl derivatives of aromatics, phenols and the like. The above-mentioned higher molecular weight olefins are especially useful as alkylating agents in reactions involving the use of Friedel-Crafts catalysts. For these purposes, it is highly desirable to use as a starting material olefins having certain molecular weights in the range of C12 and above, the C12-C2-1 group being particularly desirable from the point of view of solubility and molecular weight. Olefins which are stable under the alkylating conditions employed in the Friedel-Cratts reactions do not occur in nature to any considerable extent nor are-theyobtainable in any large volume from cracked petroleum products or even the usual polymerization products. To supplement the supplies of these olefins, they have been'formed by the dehydration of an alcohol derived'from. an oil or fat or more recently by the isothe form of narrow "ice lation by extended means of olefinic material produced by ydr carbon synth s Earlier attempts to dimerize the lower propylene poly.- mers to form principally the higher dimers using a variety of catalysts such as boron trifiuoride, aluminum chloride, sulfuric acid, stannic chloride, and the like, have failed for a number of reasons, specifically, either on the basis of the poor selective conversions and low yields of the desired dimers obtained or on the nature of the associated undesired products that have to be isolated after the reaction. In the case of aluminum chloride, for example, considerable cyclization takes place and the resulting high molecular weight products show a reduced bromine number for a given molecular weight and are particularly unstable when subjected to further chemical re.- action. When boron trifluoride alone is used as a cata lyst, some dimerization is obtained but at the same time various trimers, tetramers, etc., are formed, thus making the yields of a desired dimer so poor as to be economically unattractive. In this connection, it should be noted that this invention should be difierentiated from those processes which start with the simple olefin per so, such as propylene alone .or in admixture with varying proportions of butylene and the simple olefin is polymerized to a mixture of C6 to C12 olefins using either phosphoric acid on kieselguhr (U. 0. P. type) or boron trifluoride promoted with various agents. With the above catalytic agents, fractionationof the oily products yields a large proportion of material boiling in the C6 and C9 ranges but the yield of material boiling in the range of C. and above (C12 and higher olefin), is a maximum of about 10% on the total stabilized material, i. e., after removal of unreacted propylene. The method of the present invention is definitely distinguished from processes in which substantial amounts of olefins or paraffins containing less than 6 carbon atoms per molecule act as polymerizing reactants.

The novel method of the present invention uses a boron trifluoride-alkyl ether complex, which in the case of ethyl ether contains between 45 to 48 wt. percent boron tn'fluoride and accomplishes the desired dimerization of the low boiling polymers to high boiling polymers with negligible formation of saturated compounds, cyclized materials, or diolefinic materials. The action of the preformed boron tr-ifluoride-ether complex appears to be specific in that under-the conditions of operation, breakdown of the propylene polymers to lower boiling material does notoccur, neitheris the proportion of material boiling above the dimer excessive. The catalyst appears to act specifically for the purpose of producing a dimer of the particular Cs+ olefin reactant used as starting material. The same results are not obtained if one attempts to produce the boron trifiuoride other complex in situ by addition first of theether to the-polymer and then adding boron trifiuoridgto produce either the complex, or adding the ether separately from the boron trifiuor'ide to the reaction mixture. Some conversion is obtained but the conversions and yields so obtained are distinctly inferior to those obtained when the complex is first prepared outside the reaction zone and then added to the reaction mixture. The action of boron trifiuoride not used as a preformed catalyst even when promoted by an ether on a simple olefin of less than six carbon atoms'has been shown to be suchas-to cause-no formation of dimers. The reaction seems tobe also limited to the use of boron trifiuoride complexes with others, because other complexes such as boron trifluoride water complex or boron trifluoridephenol complex give poor yields in comparison with the boron trifluoride-ether complexes.

Ethers-which may be used to form the catalyst complexes with --boron trifluoride may be symmetrically ,aliphatic or alkoxy-type (QIHZfl-l-l'O'QZHZn-l-l) others such 3 as dimethyl, diethyl, diisopropyl ether or may be unsymmetn'c aliphatic ethers such as methyl ethyl ether, methyl tertiary butyl ether, and the like. Other ethers having similar properties may be used.

The production of the ether-boron fluoride catalyst outside the reaction-zone is not an intrinsic part of this invention and has been adequately described in the literature and in the patent art. It sufiices that the ethereboron fluoride catalyst be made before it is added to the olefin which is to undergo dimerization. It has been found that selective dimerization is obtained when using only small quantities of catalyst complex with the olefin to be polymerized. The range of ll wt. percent of catalyst complex basedon the amount of 66-012 polypropylene to be dimerized has been found to be quite satisfactory.

The polypropylene undergoing the controlled dimerization is preferably maintained in the liquid phase by controlling the reaction temperature'in the range of from 0 C. to about 100 C. Pressures in the range of from 1 to '10 atmospheres may be employed, although the higher pressures are not generally necessary for successful dimerization.

The controlled dimerization of polypropylene to give particularly C12 to C24 polymers is advantageously carried out either in batch or continuous operation with controlled regulation of feed rates, temperatures, pres sures, and catalyst complex concentration. The catalyst and/or the polypropylene feed may be added intermittently or continuously.

The polymer oil may be recoveredin any practical manner as by settling or centrifuging out the catalyst by itself or with an extractant, decomposing the catalyst with water, and separating the polymerized product together with unreacted starting material by decantation from the resulting mixture. The catalyst and its decomposition products will essentially remain in the aqueouslayer. The resulting polymer oil may then be subjected to a fractionation during which the appropriate cut is removed in order to recover the relatively pure dimerized product. In this way, the dimer is separated both from unreacted olefins and from a relatively small amount of high-boiling over-polymerized material. Y The dimerized polymers have higher chemical and thermal stability than iso-olefin polymers of corresponding molecular weight range made by less selective polymerizations of simple olefins. They also respond diflierently to treatments with chemical reagents with resulting advantages over the iso-olefin polymers in making Various products, such as in preparing wetting agents by sulfonation, in alkylation of aromatic hydrocarbons or phenolic compounds, copolymerization, etc. Considerable promise has been shown for utilization of these polymers in the synthesis of fuel ingredients, lubricating oil additives, detergents, modified resins, plasticizers, cable oils, and other compositions.

The desired dimer products obtained from the controlled polymerization of propylene'are indicated to be linear polymers having the basic structural skeleton.

with a random distribution of the double bond, usually in a tertiary position. The methyl ethylene group enclosed by the parentheses represents the recurring structural unit and n is the number of units combined.

The narrow boiling range cuts or fractions of the C9 to C39 propylene polymers, such as the separate C12 to C24 fractions, have specific commercial uses; hence the controlled polymerization is very valuable for obtaining largely any such particular cut desired.

EXAMPLE I A C9 polypropylene fraction boiling between 130 C. to 135 C. obtained by the close fractionation of a non, selective-propylene polymer product made by polymeriz.-

' ofi and the oily layer washed ing propylene over a phosphoric acid on kieselguhr catalyst at 300 lbs. pressure was mixed at room temperature with a boron fluoride-ethyl ether complex containing 45 wt. percent of boron fluoride in the proportions of 756 gms. of C9 polypropylene to 45 gms. of the boron fluoride ether complex. A slow stream of boron fluoride gas was slowly passed into the reaction mixture to replace boron fluoride which is lost on heating the mixture and the temperature raised to the range of 60 C. to 70 C. and maintained for four hours. At the end of this time, water was added to decompose the catalyst complex, the water catalyst decomposition products were drawn with sodium carbonate to neutralize any residual acidity, and the oily layer was fractionated. The results obtained are shown in column 1 of Table I, which follows, and these results indicate an overall recovery of 90.7%, no cleavage of the C9 polypropylene to form either propylene or propylene polymers boiling below the C9 range and only a small production of material boiling higher than the C18 polypropylene corresponding to the C9 dimer. The yield of dimer obtained was equal to 68.5% with a selectivity to the C19 dimer of 92%.

EXAMPLE II A C12 polypropylene boiling within the limits of 180 C. to 220 C. obtained from the same non-selective polymer products as the C9 polypropylene used in Example I, was dimerized in a similar manner to the C9 polypropylene. The overall recovery was 95% with a 63% yield of the C24 dimer, at a selectivity of 86.5%. Experimental details and inspections on the dimer are shown in column 2 of Table I. In both Examples I and II, a slow stream of boron fluoride was maintained throughout the entire period of the reaction. The amount of boron fluoride added to the reaction zone was in excess of the solubility of boron fluoride in either the C9 polypropylene reaction mixture or the C12 polypropylene reaction mixture at the temperature of operation. r

Table I lists the experimental conditions and yields for the production of a C18 and a C24 propylene'polymer from the corresponding C9 and C12 propylene polymer by this selective dimerization process.

Table I DIMERIZATION OF 09 AND 012 POLYPROPYLENE Experiment No V l 2 G 1 Polypropylene.

Boron fluoride gas bubbled in excess through reaction mixture during entire reaction period.

b Comprising some dimer.

9 Conservative yield which can be increased by taking a wider out or recovering more dimer from the lower and higher boiling fractions.

This process of this invention is to be distinguished from the prior art as exemplified by the invention of Carl S. Carlson et al., U. S. 2,588,358, wherein a similar catalyst is used for the polymerization of monomeric propylene to higher propylene polymers.

Examples 1 and 2 cited in the patent of Carlson et al. show yields of liquid polymers having a wide range of boiling points encompassing C9 to C24+ carbon atoms,

but the selectivity to the C18 polymers at conversion levels of approximately 90% is equal to only 28% and conversion to the C24+ polymer is only equal to 8% compared to selectivity respectively of 92 and 86.5% for the present invention in which monomeric propylene is not reacted with the C6 to C12 polymer which is dimerized.

What is claimed is:

1. The process for selectively producing principally a propylene polymer in the range of C12 to C24 which comprises dimerizing a C6 to C12 propylene polymer substantially free of olefins containing less than six carbon atoms at temperatures between 0 C. to 100 C. with a preformed boron fluoride-ether catalyst complex and an excess of boron fluoride.

2. The process for selectively producing C12 to C24 polypropylene polymers, which comprises dimerizing propylene polymers boiling within the range of C6 to C12 olefin polymers substantially free of lower propylene monomer at temperatures of 60 C. to 70 C. heterogeneously mixed with a preformed boron fluoride-ethyl ether catalyst complex in an amount of about 4 to 6 percent by weight of catalyst complex based on the amount of olefin polymers used, and supplying an excess of boron fluoride to the resulting mixture.

3. The process for producing selectively a C18 fraction of 275 295 C. boiling range which comprises selectively dimerizing a polypropylene fraction substantially consisting of C9 olefins at 60 C. to 70 C. with a preformed boron fluoride-ethyl ether complex and additional boron fluoride, whereby there is obtained principally C18 polypropylene.

4. The process for producing a C24 fraction of 340- 370 C. boiling range which comprises selectively dimerizing a polypropylene fraction substantially consisting of C12 olefins at 60 C. to 70 C. with a preformed boron fluoride-ethyl ether complex and additional boron fluoride, whereby there is obtained principally C24 polypropylene.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE PROCESS FOR SELECTIVELY PRODUCING PRINCIPALLY A PROPLENE PLYMER IN THE RANGE OF C12 TO C24 WHICH COMPRISES DIMERIZING A C. TO C12 PROPYLENE PLYMER SUBSTANTIALLY FREE OF OLEFINS CONTAINING LESS THA SIX CARBON ATOMS AT TEMPERATURES BETWEEN 0* C. TO 100* C. WITH A PREFORMED BORON FLUORIDE-ETHER CATALYST COMPLEX AND AN EXCESS OF BORON FLORIDE. 